1. Field of the Invention
The present invention relates to a vibrating body having plural protruding portions for a vibration wave drive device, and a method of producing the vibrating body having the plural protruding portions for the vibration wave drive device. The vibration wave drive device includes a vibrator in which an electromechanical energy conversion element is joined to the vibrating body having the plural protruding portions, and a movable body pressure-welded to the protruding portions of the vibrating body. The vibration wave drive device is used as an ultrasonic motor.
2. Related Background Art
There has been known a vibration wave drive device having a vibrator which is formed of a ring-shaped or disc-shaped elastic body, and which has one end surface provided with a large number of pectinate protruding portions, and an opposite surface affixed with a ring-shaped piezoelectric element. In the vibrator of the vibration wave drive device of this type, a large number of slits are radially defined to form the large number of protruding portions. The elastic body in this specification corresponds to an elastic material in the present invention which is a material that has not yet been pressed.
The slits function to increase the vibration displacement of a leading end of each protruding portion. The leading end surface of each protruding portion forms a friction part, and transmits the vibration of the vibrator to the movable body by the aid of a frictional force. That is, traveling-wave vibration is generated in a stator (vibrator) having an electromechanical energy conversion element such as a piezoelectric element fitted to an elastic body made of metal, and a rotor (movable body) pressure-welded to the stator conducts continuous machine motion in one direction. As one method of producing the elastic body of the vibrator described above, Japanese Patent Application Laid-Open No. H07-135785 discloses an example in which the protruding portions are pressed into trapezoidal cross-sectional shapes.
However, in the above-mentioned production method, the leading end of each protruding portion is thinned, and an area of the leading end surface of each protruding portion having the frictional surface against the movable body is liable to be reduced. In another respect, a width of the slits between the adjacent protruding portions in the circumferential direction is liable to be widened. For that reason, because a surface pressure of the frictional surface is increased, the abrasion of the frictional part is liable to increase, and there is room for improvement in the durability of the drive device. On the other hand, even when the protruding portions of the elastic body are produced through a cutting work, the width of the slits between the respective protruding portions in the circumferential direction cannot be too narrowed. This is because when a milling cutter or a grinding tool is thinned for the purpose of thinning the width of the slits in the circumferential direction, the possibility that the milling cutter or the grinding tool is damaged becomes high.